Half tone reproduction of stereoscopic photographs

ABSTRACT

A PRINTING PLATE FILM FOR PRINTING STEREOSCOPIC PICTURES TO BE VIEWED THROUGH A VERTICAL LENTICULAR SCREEN IS PRODUCED BY TAKING A STEROSCOPIC CAMERA NEGATIVE THROUGH A SMALL APERTURE LENS WITH A SCREEN IN FRONT OF THE FILM. THE SCENE IS SCANNED ACROSS THE INTERPUPILARY ANGLE WITH A MECHANICAL SCANNING CAMERA. A PROJECTION LENTICULAR SCREEN IS PLACED IN FRONT OF THE CAMERA NEGATIVE AND THE LATTER IS PRINTED THROUGH A GRID TYPE HALFTONE SCREEN IN FRONT OF A PRINTING LENTICULAR SCREEN AND THE SENSITIVE PLATE FILM. A MECHANICAL SCANNING PRINTER HAVING A SMALL APERTURE LESS PRODUCES &#34;ISOFLAGS&#34; ON THE PRINTING PLATE FILM. THE HEIGHT OF THE ISOFLAGS AT ANY POINT IS PROPORTIONAL TO THE BRIGHTNESS OF THE CORRESPONDING ORIGINAL IMAGE; AND THE PLATE IS PREPARED FROM THE PLATE FILM FOR PRINTING THE ISOFLAGS BY ANY CONVENTIONAL PRINTING METHOD, SUCH AS LETTER PRESS, GRAVURE, LITHOGRAPHY, ETC. SCREEN TO RE-ESTABLISH THE ORIGINAL SCENE AS A THREE DIMENSIONAL PICTURE. A METHOD IS ALSO DESCRIBED WHEREIN WIDE LENS TAKING AND PROJECTION CAMERAS ARE EMPLOYED.

D. F. WINNEK May 30, 1972 HALF TONE REPRODUCTION OF STEREOSCOPIC PHOTOGRAPHS Filed 001'.. 19, 1967 ATTORNEYS D. F. WINNEK May 30, 1972 HALF TONE REPRODUCTION OF STEREOSCOPIC PHOTOGRAPHS l5 Sheets-Sheet 2 Filed OOb. 19, 1967 omNu n INVENTOR. DOUGLAS F, WINNEK ATTORNEYS D. F. WINNEK May 30, 1972 HALF TONE REPRODUCTION OF STEREOSCOPIC PHOTOGRAPHS l5 Sheets-Sheet 5 Filed Oct. 19, 1967 mDPOru 0252s.

NVENTOR, a DOUGLAS FWINNEK @ff @c ATTORNEYS May 30, 1972 D. F. WINNEK HALF rPONE REPRODUCTION OF STEREOSCOPIC PHOTOGRAPHS Filed 001'.. 19, 1967 l5 Sheets-Sheet Q (A) (B) TAKING PICTURE INVENTOR.

DOUGLAS F. WINNEK AT 'VORNE YS May 30, 1972 D. F.r WINNEK 3,666,465

HALF TONE REPRODUCTON OF STEREOSCOPIC PHOTOGRAPHS Filed Oct. 19,1 1967 15 Sheets-Sheet 5 TAKING CAMERA NEGATIVE PROJ ECTION SCREEN AT TORN E YS May 30, 1972 HALF TONE REPRODUCTION OF' STEREOSCOPIC PHOTOGRAPHS 15 Sheets-Sheet 6 Filed OCL. 19, 1967 VlSUAL REGlSTRATION TECHNIQUE n NFH D! WMS A u mm. ,n no. u e wwf ATTORNEYS D. F. WINNEK May 30, 1972 HALF TONE REPRODUCTION OF' STEREOSCOPIC PHOTOGRAPHS l5 Sheets-Sheet 7 Filed Oct. 19, 1967 INVENTOR. DOUGLAS F.WINNK BY @www ATTORNEYS D. F` WINNEK May 30, 1972 HALF TONE REPRODUCTION OF STEREOSCOPIC PHOTOGRAPHS 15 Sheets-Sheet 8 Filed Oct. 19, 1967 INVENTOR. DOUGLAS F. WINNEK ATTORNEYS D. F. WINNEK May 3o, 1972 l5 Sheets-Sheet 9 Filed OCT.. 19, 1967 G mm wc EC a V8.2.. v l: v a m m a Mw \l IA.. ad.

M Z u a fl. a4. l M) n "IIB a /anJ/x f. E a-..

-F'IGJZA INVENTOR ooueLAs nwmuex d Maan,

ATTORNEYS May 30, 1972 D. FQ WINNEK HALF' TONE REPRODUCTION OF STEREOSCOPIC PHOTOGRAPHS Filed 001;. 19, 1967 l5 Sheets-Sheet l0 I6 IOO UND HALFTONE SCREEN TAKING CAMERA NEGATIVE ITIIT'IELATION l I E NEUTRAL BRIGHT DIM HALFTONE SCREEN, I6@ H5 PLATE NEGATIVE OO UN HALFTONE SCREEN INVENTOR.

DOUGLAS F. WINNEK BY vJa/ M ATTORNEYS May 30, 1972 D. F. WINNEK 3,666,465

HALF TONE REPRODUCTION OF STEREOSCOPIC PHOTOGRAPHS Filed oct'. 19, 1967 15 sheets-sheet 11 F"IE .lq A

HALFTONE GRI li I\ LENTICULAR .I SCREEN BRIGHT NEUTRAL DIM l Vr* n di" GBUND ma :|un :www 4B GLASS i I ...IJ Lt... il

"""" C33? CS Q 81 E l? r: DQ INVENTOR L40@ Hiob DOUGLAS awmsx F- 1 E 1 El BY JU @M @5V/zw ATTORNEYS May 30, 1972 D. F. WINNEK A 3,666,465

HALF TONE REPRODUCTION OF STEREOSCOPIC PHOTOGRAPHS Filed Oct. 19, 1967 15 Sheets-Sheet l2 gli- I [3 1 E'. NEGATIVE- f HOLDER LENS 2 l )Il ,TI 56 20N 50o.

36 TOOTH GEAR PRI NT HOLDER 72 TOOTH GEAR GO GEAR MOTOR NVENTOR. DOUGLAS F. WINNEK BY Mam/mn,

ATTORNEYS I May 30, 1972 D. F. WINNEK 3,666,465

HALF' TONE REPRODUCTION OF STEREOSCOPIC PHOTOGRAPHS Filed Oct'. 19, ,1967 15 Sheets-Sheet 13 B ^`B- FIELIB W 6 A\ INVENTOR DOUGLAS F. WINNEK ATTORNEYS MaySO, 1972 D. F. wlNNEK 3,666,465

HALF TONE REPRODUCTION OF sTEREOsOOPIc PHOTOGRAPHS Filed Oct. 19, 1967 l5 Sheets-Sheet 14 INVENTOR DOUGLAS F. WINNEK AT TORNE YS May 3 0, 1972 D. F. WINNEK 3,666,465

HAM" TONI-1 REPRODUTION OF STEREOSCOPIC PHOTOGRAPHS Filed Oct. 19, 1967 l5 Sheets-Sheet l5 INVENTOR. DOUGLAS F. wlNNEK HVJ-[MM ATTORNEYS 3,666,465 t HALF TONE REPRODUCTION OF STEREOSCOPIC PHOTOGRAPHS Douglas F. Winnek, Palo Alto, Calif. (10450 W. Loyola Drive, Los Altos Hills, Calif.

Filed Oct. 19, 1967, Ser. No. 676,484 Int. Cl. G03f 5/00; G03c 9/00 U.S. Cl. 96?-45 f: i 8 Claims ABSTRACT F THE DISCLOSURE A printing plate film for printing stereoscopic pictures to` be viewed through a vertical lenticular screen is pro- `duedby taking astereoscopic camera negative through a small aperture lens with a screen in front of the film. 'I'he scene isscanned across the interpupilary angle with a mechanical scanning camera. Av projection lenticular screen is placed in front of the camera negative and the latter is printedthrougha grid type halftone screen in front of a printing lenticular screen and the sensitive plate film. A mechanical scanning printer: having a small afperture lens produces soags on theprinting plate film. 4The height of the isoflags at any point is proportional to the brightness ofthe corresponding original imagejand theplate isprepared from the plate film for printing the isoflags by any conventional printing method, `such as letter press, gravure, lithography, etc. screen to re-establish the original scene as a three. dimensional picture. IA method is also described wherein wide lens taking andfprojection cameras are employed.-

eRoss InFEIjiENoI-:ro `IznlgieninnAPI'LICA'rIoN's I9 66,. `.discloses and c1ain` 1s a` projection printing process using lenticular screen s which. ar e ,r elati vely inclined in their respective planesin order "to minimize moire pattures using polarized picturehalvesviewed.throughpolarized glasses. A ffhalftonef. linev screen interposed between arsved lnticnlar lmand a negatvetobe copied, with the' lines `of the sreenperpendicular t`o the lenticulations.

A H owe 3,161,509 recognizes the problems introduced in attempts to'use ordinary halftone plate making processes for stereo pictures formed with'jlenticular screens',- in that an unacceptably fine halftone screen is required, be ganse' if the Width f a. Stereo dat ,approaches that bf. a lenticulethe'stereo discrimination is small. The solution Proposedis the use' of linev halftones for printing the; imag? having a'widtli only' slightly smaller than the width of the lenticules andextending perpendicular to thejlatte'r. v No scanningfor the production o f isoflags witha regular type Ihalftone' screenin projection printingis described.

' SUMMARY. OF. THE INVENTION.r`

The ultimate benefit of this invention lies in the, produc'- tio`n of a' print ing plate resulting from a stereoscopic camera and projection printing technique of the type wherein a lenticular screen is employed in the taking camera, as well as infront of theultimately printed picture, for viewing the latter. Ai printing plate is produced for'makingl prints which give a true three dimensional, stereoscopic picture'when viewed through a lenticular screen. Printing plates of 3,666,465 Patented May 30, 1972 'icethis type have heretofore required the use of a very fine halftone screen (e.g. 300 lines/inch) and therefore limited by commercial practice to the lithographie process, and even so only a relatively few bits of stereo information are provided behind a lenticulationof the viewing lenticular screen by each aperture in the halftone screen.

On the other hand the plates of present invention can be letter press, gravure,. lithographic or other normal printing plates since coarser halftone screens can be'used while retaining the full 3-D effect.

In accordance with the present invention, the image behind each lenticulation formed by light passing through an aperture in the halftone screen grid is a band or continuum of vertical line images.` The continuum of images in each band that was behind a halftone screen aperture y and a lenticulationduring'projection printing,'wi ll, for

sake of convenience, be referred to as an isoagJ Each line image in an isoflag represents a view of the Original scenefrom a particular scanning angle. The scanning angles for all lenticulations total to a viewingk Vangle having a base line of a length'comparable to or'preferably greater than the interpupilary distance of the eyes. Scanning during both taking the picture andproj'ection printing it can be either mechanical or optical (wide lens scanning).

The r vertical dimension (that along a lenticulation) of eachl line image making up an isoag is proportional to the intensity and exposure time of the light projected through the corresponding aperture in the halftone screen. The process of making the plate film or plate copy will Anot be described since the plate is made from the plate film by known methods. i The preferred method of forming a plate film bearing isoilags involves the use of mechanical scanning taking and 'projection cameras. The original Scene is exposed through a small aperture lens which exposes the negative through a lenticular screen. Both lens and the films`creen sandwich are moved uniformly during exposure atrates proportional to their respective distances from the focal plane of the scene. The optics of the taking camera' is such that in sweeping through the scanning angle, the'images formed by a central (optical axis) object in;l the camera focal plane fill a band of the camera negative behind the central lenticulation.

y The camera negative is printed through a projection lenticular -screen of the same pitch asthat used in the taking camera. The plate iilm on which isoflags are to be formed is placed behind a printing lenticular screen and the latter,.in turn, is placed behind a conventional grid type halftone screen. The light projected through each halftone screen aperture, as modified by the lenticular printing screen, produces the isoilags during scanning.

Instantaneous taking and projection cameras having wide, lens can also be used to produce isoflags. The camera lens should have large horizontal apertures, corresponding to the interpupilary distance between the eyes, or preferably more for good three dimensional effect. The taking camera forms pseudoscopic negatives, that is, negatives wherein near objects appear faraway and vice versa. However, a true or orthoscopic plate is produced by selection of the projection printer optics.

BliEF DESCRIPTION oF THB DRAWINGS FIG. l is a schematic flow diagram illustrating a processforl printing three dimensional pictures under the invention.

`FIG. 2'is an optical diagram showing various critical dimensions of a lenticular screen.

FIG. 2A is a diagram drawn to relative scale showing the viewing angles and F numbers of variously proportioned lenticulations.

FIG. 2B is an optical diagram showing how a bundle ofparallel rays is acted upon by the screen vand how a bundle of rays passing through the center of curvature act. i

FIG. 3 is a Aperspective diagram illustrating the taking of a three dimensional picture.

FIG. 3A is a top edge view of a film and lenticular screen assembly illustrating the incidence of various light rays thereon. i

` FIG. 3B isan optical diagram resembling that 'of FIG. 3 illustrating the taking of a picture.

FIGS. 3C,.D and E are greatly enlarged diagrams showing the incidence of'various rays on a moving lenticular screen.V The iilm has been omitted in these views for clarity.

FIG. 4 is a schematic perspective diagram showing the projection printing' process. v i

FIG4A is an optical diagram of the projection printing process showing the action of a single ray passing through the centerfof a-curvature of a projection lenticular screen intercepting a traveling lens at three positions.

FIG. 4B is an optical diagram showing how 'the lenticula'r screen gathers light froml a single point on the film for passing through a` projection lens. The lenticular' screenA normally used in the projection processvof'the present invention is not shown in either FIGS. 4A or 4B for clarity. Y

FIG. 5 lis an optical diagram showing the printing process illustrated in FIG. 3. V

FIG. 5A is an enlarged fragment of the optical diagram` of FIG. 5 with the projection lens 21 at the left ofits travel.

FIG. 5B is a greatly enlarged fragmentary portion of the diagram of FIG. 5A.

FIGS. 5C and 5D are views like those of FIGS. 5A

and 5B but with the projection lens 21 at the right hand of its travel. FIG. 6 is an optical diagram showing the visual registration technique for registering a lenticular screen with a lm containing stereo information.

FIG. 7 is a perspective illustrating a viewing of a stereoscopic picture.

FIG. 7A is an optical diagram provided forfillustrating the lprinciples of how a stereoscopic' picture is formed. FIG. 7B is an enlarged version of the optical diagram of FIG. 7A showing certain individual lenticulations of the screen. ,L p

FIG. 8 is a'schematic diagram showing a conventional printing process using a ne, halftone screen for producing a plate negative that contains stereoscopic information.

FIG. 8A is a plan view of the negative producedbyithe conventional printing process of FIG. 8.

FIG. 9 is a perspective diagram illustrating the elect of a lenticulation on a bundle of light rays.

FIG. 10 is an enlarged optical diagram illustrating the FIG. 13 is a schematic diagram highly stylized showing how the isoags may assume various shapes depending upon the objects depicted and their brilliance. f

FIG. 14 is a highly enlarged presentation ofthe isoflags on a 100 line lenticular screen where the illumination was predominantly dim;

FIG. 14A is a view like 14 where the illuminationV was* predominantly bright.

FIG. 15 is a fragmentary enlarged section.: showing lm and screen holder of a projection camera embodying the invention. 't n FIG. 16 is a perspectivezdagram of aprojection camera suitable `for carrying out `the yprocess of the present invention. u y

F-IG. 17 is an optical diagram showing the exposure of a pseudoscopic negative with an instantaneous camera.

FIG. 17A is-.an enlargedoptical ydiagram atI the camera negative.- Y .Y

FIG. 18 is an axillary compressed optical diagrarnlike that ,of FIG. 17, showing additional principal krays.l

FIG. 19 is an optical :diagramllike ythat -of-FIG." 17 showing an instantaneous `projection printer.' 'i

v FIG. 19A is'anA enlarged diagram similar toFIGQ 17A showing the camera negative, the printing Aplate filml and the halftone screenw .FIG. 20 is an enlarged, axially' compressed optical diagram of the printing proces's shown in FIG. 191show4'- ing additional principalrays;` f

FIG.` 21 is a schematic diagram illustrating the lviewing of a stereoscopic print made --fromhtheplatiilm'of FIG.` 19. i DETAILED lDESCRIPTIONy The detaileddescription of theinvention which follows will begin with a descriptionv of a sequence ofoperations from the .taking of the stereoscopie'l-picture (the `-word stereoscopic to .be hereinafter. abbreviated -as."stereo for simplicity), to therviewingof a halftonereproduction of that picture.

The 'sequence to be described willfbe relative to a series of steps for making a stereo picture, which sequence represents only one of several techniques available-for taking advantage of the printing platelm making process of the present invention. Except for an initialblock diagram of a system embodying the invention;` it will be found that the description initially runs through a-series of operations necessary for the -reproduction'and viewing of 'stereo pictures as photographs, order to establish" certain principles'relativeto' the phenomena: of lenticular screens in stereo photographs. Knowledge of these phenomena is necessary' for ready understanding of the invenf tion in' the halftone printingaspect's of this invention. l

Following the description of the principles lof stereo lenticularscreen photographyhisfa description of the principles of a'rhalftone reprodutcion process embodying the present invention, rfollowed vby adiagrarn of a scanning camera `suitable for vcarrying out the ijrn/entlonf."fy

The nature of the drawing Ain thediscussion thatlfollows is necessarily schematic and stylized. Also,` because ofthe avast discrepanciesk in distances and dimensions inf Volved, e.g., the camera to objectdistan'ce as Acompared to'thewidth of an individual lenticulation infthe stereo screen, true scale cannot'befmaintained inthe drawings if information as to` th'e`inventi`on is to be visualized; It is also to be understood'that as tojthe constructionz and optics of various cameras, printers and so forth that are necessarily involved inpracticing the invention',rno1attempt ismade to give working drawings onthe likeito;'the,se instrument's. Once principles are known, y.thepresent',invenf tionVA can be ltranslated bythosed skilled inthe-Y optical camera, and printing arts into commercially *usable machines without employing anything more than the skill of the calling. Anyuspecial features of these ,opticalv instrufl ments peculiar to the,presentinventionwill be presented v tolftheextent necessary to enablevvonerskillecl A.in theffart to .construct an actual.deyicevfWeregit not forfthis ap, Preah the-,inventicn would be collcealcdA b mass of materialalreadyfin the priorlart SYSTEMTIAGRAM `21=1G.61'-is a blockl diagram or a systenfi1emanayinv the invention, the 4sequencelof steps being "ondcted' by dashed flow arrows. Thefirst stp is to take a stereo picture through a lenticular screen. In the system to be described in detail as illustrative, this involves the use of a scanning camera indicated generally at 10, and shown diagrammatically in FIG. 16. The camera has a small aperture lens 11 and incorporates a lenticular screen 12, which will be referred to as the taking screen. The taking screen abuts the camera film 14 and focused on the film is an -intermediate object A, there also being a1 more kremote object B and a near object C, the presence of which will be .employed to illustrate the principles o the stereo photography involved.

In the example to be described in detail, the taking lenticular screen 12 will have 100 vertical lenticulations to the inch, which will be referred to for convenience, as a 100 line screen, each line, of course, referring to an individual lenticulation. Each lenticulation acts as a miniature cylindrical lens, and in the example being given the ;f/ number of the lenticulations of the taking lenticular screen 12 will be given as f/4. The taking camera film is developed to form a negative, also indicated as 14 and the next step is to register the negative 14 with a lenticular` projectionV screen indicated at 12a. The manner in which this registration can be effected will be described briefly as the discussion proceeds. The lenticular screen 12a must have the same pitch as the taking screen 12, that is, it must be alOOlne screen, in the example being given. The f/number of the projection screen 12a need' not be the same as that of the taking screen 12, but in the example it will beassumed that the projection screen 12a also has an f/number of f/4. The registration referred to is simply the positioning of-the projection screen 12a on the. stereo negative 14 so that the boundary lines between lenticulation images on the negative 14 coincide with4 the boundary planes between the lenticulations of` the projection screen 12a.. f

j After registration, the projection screen 12a is taped `moved synchronously during exposure.y The printing screen 12b need not be of the same pitch as the projection screen 12a. For example, instead of rbeing"a lOOfline screen, the screen 12b could bea 150 line screen; In the example being given, however, it will be assumed that the printing screen 12b is af 100 line screen and:` that its f/number is f/4; In` the projection printerg-any isoilag print is made which contains all tliestereoinformation necessary for the production of a stereo-printing press print that gives the same stereoscopicview as that given by an stereo photograph when viewed through a lenticular screen. l v .f After completion of the projection printing operation, the printfilm 14a is developed and then used in accordance `with conventional commercial printing practice' in order to make Va halftone printing plate. This printing plate includes the isoa-gs that contain all the stero information necessary to give theI desired effect from the nal print. The halftone plate 14b is then transferred to a printingpress, illustratedv in highly diagrammatic form at 22, and prints 18 are procduced. -In order to view the prints 18 stereoscopically, it is llirst necessary to register each print with its individual viewing lenticular' screen and bond the screen and print together. The viewing screen 12e must hve the same pitch as that of the printing screen 12b. However, the f/number of the lenticular viewing screen 12eI can be different than that of the projection screen 12a. For example, if the printing screen 12b were a line screen, then the lenticular viewing screen 12c would also be a 150 line screen, but in order to provide a wider viewing angle the f/number of the viewing screen 12.` could be f/2. The smaller f/number also results in a lenticular screen which is thinner, an f/Z lenticular screen being only half as thick as an f/4 screen with the same number of lines per inch. A thin lenticular Viewing screen is particularly desirable in case the stereo print is viewed in abook, magazine or the like, as illustrated in the last step of the diagram of FIG. 1.

As will be described in detail, even though the halftone screen 16 employed during the projection printing step need not be an unusually tine mesh screen, the formation of isoags during the projection printing process insures that all of the necessary stereo information is present in the print 18 and hence, when the picture assemblage 18, 12e is viewed, a good quality stereo picture is presented.

PROPERTIES 0F LENTICULAR SCREENS j 1 FIGS. 2, 2A illustrate Various properties of lenticular screens involved in the present invention. In addition, reference is hereby made to the patent to Winnek 2,562,- 077, incorporated herein by reference, for further explanations of the technology involved in lenticular screen stereo photography. It is contemplated that these screens are made of a transparent, exible plastic Ymaterial having an index of a fraction n in order of 1.5. Materials suitableV for these screens are polyvinyl chloride, polyethylene, acrylics, and many others with suitable optical properties.

Fundamental formulae of these screens are given at the left ofl FIG. 2 and their derivation is familiar to those skilled in the art. The viewing angle a requires some explanation. Referring to the diagram of FIG. 2, which isa greatly enlarged fragmentary section of a lenticular screen 12 viewed from its top edge, the screen can be considered to be formed of a series of cylindrical lenses, having a cylindrical outer surface 26 and a planar inner or back surface 28. The dotted lines 30, indicate hypothetical boundaries between each of the lenticulations. The radius of curvature R and the index of refraction n are selected so that the focal plane of each lenticulation for parallel light rays is at the rear surface 28 of the screen. The viewing angle a is boundedby the extreme rays passing through the center of the radius of curvature R of the screen and terminating at the junction of the lenticular edges 30 and the rear of the screen 28 as shown. These rays Aare normal to the surface 26 and hence are not refracted. Each cylindrical lens or lenticulation provides a `unique picture element containing a continuum of stereoinformation images across the rear face 28 thereof, and the viewing angle a within which the information behind each lenticulation can be seen is defined by the extreme rays passing through the center 27 of the radius Rand extending to each of the corners of each lenticu1 ation,these corners being the intersection of the hypothetical yboundary planes 30 and the rear face 28 of the screen.

FIGfZA is a diagram of two lenticulations, various surfaces, thereof being drawn relatively to scale. The purpose of this Adiagram is to indicate the physical dimensions ofthe lenticulations in relation totheir f/numbers, and also indicatey the corresponding viewing angles a. The index of refraction is assumed to be equal to 1.5, and it is believed that diagram 2A is self-explanatory.

FIG, 2B illustrates certain properties of the lenticular screen z`with the lenticulations thereof acting as lenses. At the left of FIG. 2B, parallel bundles of rays G andH are` seen entering adjacent lenticulations at divergent angles. In this, and in other views the mythical boundary planes 30 between lenticulations is drawn in solid lines for simplicity of illustration, it being understood that the screen is actually one solid sheet of transparent material. All of the parallel rays of bundles G that are encompassedby one lenticulations will come to focus at a point G. behind that lenticulation (neglecting aberrations). The point G also intercepts a ray passing through the-,center of curvature 27, shown in dashed lines. Thebundle-of rays Gris also Ashown, as includingy a ray G1 which strikes an adjacent lenticulatiom This ray .will be refracted-'andstrike a baseof thescreen 28 at a point G1 behind that lenticulation. The points G.' both occupy the samerelative-.positions. on the lenticulation bases 28. Similar considerations can be applied to the bundle of raysH strikingvthescreen at a different angle of incidence. 1 t

At the right of FIG. 2B, a series of divergent raysis shown, all .passing through the center .27 ofV the radius of curvature R vof the screen. The series of `rays l includes a number of rays vwhich lie within theviewing anglea ofv FIG. M2. These rays are all unretracted, and all but one falls within thedwidth w-of the base .ofthe lenticulation at the base 28, Oneofthese rays J1 diverges from a normal rayy through center.27 byanangle greater than half the viewing angleA a (Whichisassumedto be 289 in this example), and `hence-'passesright-through the lentiulation .just referred to. and terminates at the b ase of an adjacent lenticulation at point J1. Thus, Athepoint J1' would bevviewed onlyalong theline 11,or alonga nearby parallel lineemerging'from the` samelenticulation, or. at a different, angle through an adjacent lenticulation `as shown by J1. Thus,although light passes through the. outer surface 26 of one lenticulation, theimage is sometimes at the-base of another. The lenticular lscreen illustrated in FIG. 2B in an f/2 screen. t v

The point to be made relative to the present -inveu-` tion in FIG. 2B is that as indicated in the left-hand figure, if one were looking into a screen at a givenangularity, i.e. with one eye as long as that angularity is maintained within the Width of a lenticulation, the viewer willalways see one uniquely positioned point in back` of a given tions exist whether light is incident upon or emanating lenticulation. Conversely, if one were to` lookthr'ough the screen at varying degrees of angularity, the backof the screen would -be scanned. Of course, similar vcondi- FIGS. 3 to 3E illustrate the principle of one mode of taking a stereo picture. In the. technique to be de-A scribed, the picture is taken with a scanninglcamera having a relatively small aperture lens (about f/SO) although generally speaking, the nature of the taking camera is not critical to the present invention. For example, awide lens camera such as that disclosed in the aforesaid `Wi'nnelrv Pat.` No. 2,562,0 77 could also be employed for takingl the lpicture and making the stereo print 14a as vdescribed later. I The principle of producing a stereo picture can bestimrnarized by stating that a picture is taken so that the imagesmof the object lield'from the differenti "viewing angles are recorded at unique positions onuthe jiilmjv in back of the lenticulations resulting in a contiiiuumlfofl' pictures andthe viewer of the tinal picture inwturn; sees only two of these different pictures at any time the` particular pair of pictures seen varying asf'the `viewer moves his' head back and'forth laterally relative to the picturei One of 'the principal purposes of this"iraiven'tiori'l is to retain as much as possible of this discrete informa'- tion, in the printing press reproduction of stereo1 pictures.`

counting to the left and negative numbers'countingto" the "fright Thus', with a- 100 line screen, a lentic'ulation' l-l-'1'16 would be 1.16 inches to the left off'theffcenterf 1.75 inches to the 'right of the center of the'screen-:tifr

LIn FIG. 3,'a convention is adopted wherein three objects ,Ap-'B and C `are exposed; along the principal or central axis of the picture plane; IIt will1be assumedthat object y=Awillzbe-the vpoint of interest and that .the camera is=`focused on object A1 Stated fdiierently, Aif a viewer focusedron A'land moved'hishead `from side toside, his .-views fof'fobjectsB and C would move `relativeto A, ar1d'-in'opposite directions. vLines emanating froml` these objectsat various angles of'incidence from thecentral picture axis are indicated as (A), (B), and .(C), andl these lines .are shown'at several {positions-of the camera lens'and iilm.' f fr t... t The convention 'is further `adopted thatt-the images of thehincide'ntlight rays of the various objects (in or out fo'f focus),are given'circled numbers. k-l-Each of. these image points is unique, representingy the image ofanpobjechat one and only one position of `the,sereenaridilm ass'emblyyandofrthe lens. During exposure of the picture with the taking camera 10, both the lens 11 and the lm and-screen assembly 12 and 14. are movedy laterally at linear rates whichfbear a constantratio to. each l other (seefthe,.notationsv on FIG.V 3B). -As the picturev is taken, the images'v from a @given `object not inthe plane of principalV focus; aresuccessively formed on adjacent lenticulationsf'from onegsidetl of vthe screen -to the center of thescreenand then-fonte the other side` of the screen. Thetlenticulations, functioningfas indicated in FIG. 2B, render; the images behind each lenticulation unique, and generally nor1superimposed.--E Y,

FIGaBA is a diagramof the film and-screen assembly 12, `14 `drawn on a larger scale, showing -all of the images 1 to 7 produced =bythe `scanning camera and indicating the objects from which these images emanate.

`FIG. 3B is an optical diagram showing the; information illustrated inperspective in FIG.3 and alsofgiving dis` tances Ainvolved relative to the objects, the scanning camera: lens and screen travel..Thesedistances; are given merely by l,way lof example IandgivenA for purposes of explanation;ThefdistancesL of 'lens' and -screen travel dependxuponthe distancefrom-the lensuto the principal (focused) object A, as well as the distance between the screen andthe lens and the f/number of the screen. As will` be yseen (FIG.: 16).'.assuming1 a distance. to the principal objectA, `and a lens 4spacingr'oxn the screen,

film combination' 12,. 1j4 a'camera cant-hermade to'scan` the vieu/ byemploying a-simplerack and pinion assembly. Ins-this and in other-views, the lens is :shown asA a simple double convexlens. If ,more `complex. lensesnver'e:` used, the optical center. of thelens assembly'swould form th referenceplanefor distance measurements. Qpti'calvly,. whentheulm and screen are atuthe left or point'X. inFIG. 5B,l the rays (C) from the near. object C are,.directed by alenticulation to the filnratapoint 1 whichaisinthe, left halfA of the film; the ray (A) `from thefprincipalfobjeet A'will be focused on thevfilm at 2which is'funderV lenticu1`ation`#0 at `the optical'center of `they iiln; vand lthe ray .,(B) from the remote object Bv wil b'e'imaged f at point 3` ontherght h'alf lof the the Y position `bf the .screen 'and `film Vwhich is alongA the Lal or picture axisftherays (A, B, C) from all three v l A, B ad'C (it nearer objects do not eclipse'those behindyfthem); "'vi/ ilPbe'4 imaged by the center" lenticulation #Wo he same spot,l point 4; Atthev right handp'osition-y Z o'"thlelfiilm,l 'conditions will besymmetrically reversed fromY those' ofposition X,"in that points 5, 6 and'7 repre-` seiwitfthei^ images of rays' from objects B, A` and C, respectively," `and positionally "complementary to" points y3, 2' ari'dLfrefspectivelyt t In order*dundrstandsthe significancevof the optical diafgrarrisCifFIGISSV and 3B a series'ofenlargedexplana# tr'y views of the'fscreen` is-prese'ntedin FIGS; 3C, D and E.In these `figures,ithe iilm has been omitt'edfor clarity andonly lenticulatins under discussion are shown; The: sizeof the -lenticulation's hasvbeenexaggerated inthese; figures' for purposes of illustration.:ReferringtoFIGLSC it cau be seen how the ray (C) images at point 1 passing through lenticulation #+174 and continuing on into the base portion of lenticulation #+175. 'Ihe principal ray only is shown here, that is the ray that-passes through the center of curvature of t-he surface 26 of the lenticulation. This is true in the other illustrations in these iigures, but the aperture of the camera lens 11 is so small, that other rays from a given object come in almost parallel and image at the same point, as seen at the left of FIG. 2B. It will be noted that the image represented by polnt lis near the right hand edge of lenticulationr#+175. The rays (A) will be focused by lenticulationv at point 2 at the left hand edge of the base of that lenticulation. The rays (-B) will be focused` byjlentlculation #-116 at a point 3 near the left handedge of the base of that lenticulation.` y l FIG. 3D merely illustrates what has been mentioned previously, namely when the screen 12 is on the normal or picture axis, the rays (A), (B) and (C) image at the center of lenticulation at point 4. This ligure also illustrates the position of image 2 of object A that was formed when the screen was at the left-hand position X during exposure.

FIG. 3E. is a third enlarged diagram showing the screen at position Z and now it can be seen in more detail how the rays (B), (A) and (C) are imaged at points 5, 6 and l7, respectively. FIG. 3E likewise indicates, 'for purposes PROJECTION PRINTING- In-accordance with the plan of this explanation the projection printing process illustrated in .perspective in FIG. 4will first be explained in connection with a process wherein isoli-a-gs are not formed, that is, when the halftone screen 16 (FIG. 1) is omitted from its positionatthe printing screen and the print nlm. Production. of isoags by the halftone screen will then be explained. Y

" The printer 2,0 includesascanning camera which operates in accordance withrthe same general principles as the scanningipicture taking camera 10,'and` a` simplified perspective diagram'of the printer appears FIG. 16.` The same principles ofconstructioncan be used in designing the picture taking scanning camerali). p e As" previously described in connection,y with .thel block diagram of FIG. 1, before projection printing 'under the present invention a projectionv screen 12a, which must b e of the same pitch as thetaking screen 12 (aI 100 `line screen in the example being described), is registered with the developed negative 14 made by the taking camera. rI his assembly is illuminated by conventional means shown schematicallyin the form of a lamp 34 anda light diffusing plate 36, FIG. 4. The printer lens 21 which scans the taking camera negative 14 4and its lenticular screen 12a is another small aperture. lens (e.g. about lN50) and is moved at a predetermined rate selected in accordance with the physical distances involved between the two iilms and the lens, the lens aperture, sensitivity of `film 14a, etc. to provide the desired exposure for printing behind each lenticulation of the printing screen,12\b. As mentioned, the pitch of the printing screen ,12b need not. be the same as that of the projection screen 12a because a new picture of the taking camera negative 14 is now be,- ing made. However, forsimplicity of illustration, it will be assumed that the printing screen 12b is also a 100 line screen. In the projection printing operation the scanning process s such that the small aperture. lens 21 suc- 10 cessively scans images behind each lenticulation of the projection lenticular screen 12a and focuses these images on the lenticular printing screen 12b. The latter duplicates the array of images behind each lenticulation of the negative 14 on the print film 14a, thereby making a true or orthoscopic stereo print. i

FIGS. 4A and 4B illustrate some of the principles of the scanning type projection printing described, these views omitting the lenticular printing screen 12b for purposes of initial explanation. FIG. 4A shows how principal rays passing through the center of curvature of a given lenticulation but emerging from the taking camera negative 14 at different ang-les relative to the picture axis will strike'the plane of the print lm 14a at different positions along the lateral extent of this plane. It will be noted that these principal rays cross at the center of curvature of the lenticulation illustrated, so that the order or sequence of both sets of images, as viewed from in front 14 or 14a is unchanged. Thus if the iilm 14 is orthoscopic, the nlm 14a will be also, insofar as the relative positions of the images is concerned.

FIG. 4B illustrates the principle previously mentioned in connection with the left-hand diagram of FIG. 2B. Assume a given angularity of the principal ray passing through the center of curvature 27 of a lenticulation in the projection screen 12a. Light from a point image on the camera negative 14 from which said ray emanates will be collected by the'overlying lenticulation and projected as a bundle of parallel rays. This bundle of rays will, in turn, be focused by the printing lens 21 onto the print lm 14a, as an image of the original point being described. The laperture of the lens 21 is so small (e.g. f/SO) that the convergence of the rays leaving the lens 21 is insigniiicant (e.g. about 1 minute of arc total angle) so that the action of the printer can be explained on the assumption that these rays are actually parallel.

FIG. 5 is an optical diagram corresponding to the perspective of' FIG. 4 illustrating the geometry of making the projection print. In the example given the distances between the projection screen 12a and the scanning lens 21 and the printing screen 12b and that lens are assumed to equal 27.7 inches. The convention, relative to numbering of point images previously adopted, is repeated in FIG. 5 and succeeding pictures except that the image of point 1, for example, on the taking camera iilm is given the number 1a on the projection film. FIG. 5A presents a portion of the optical diagram of FIG. 5 drawn to slightly larger scale and is self-explanatory. Only principal rays appear in FIG. 5A, but, as mentioned the lens 21 has a small aperture and hence other rays making up the images la, 2a, etc., can be assumed to enter the lenticulations of the projection screen 12b as parallel rays.

FIG.l 5B is a greatly enlarged, non scaled diagram showing the phenomena illustrated in FIG. 5A. The image 1V from object C is projected by the lens 21 onto lenticulation #+174a and is focused at the base of #-i-l75a as lan image la. The image point 2 from the picture plane vobject A is also aligned With center of curvature 27 of its lenticulation #0 and the center of the lens 21, and hence appears as an image 2a at the left edge of lenticulation#0a of the projection printing screen. The same conditions relative to the camera negative image 3 and its print 3a for the remote object B, likewise obtain. As indicated at the projection screen portion of FIG. 5B, light'A rays will also be projected from points 7, 6, 4 and 5 in theA direction from which these images were made in the taking camera 10 as Well as in other directions (not illustrated), However, in projection, these latter rays miss theaperture of the projection lens 21 and do not reach the printing screen and film. The conditions are just as if the images 7, 6, 4 and 5 were not present in the particular lm and printing screen position of FIG. 5B.

FIGS. 5C and 5D correspond to FIGS. 5A and 5B just described, but with the printer elements disposed vat the righthand position of their scanning motion. As seen in these figures the taking camera negative points 7, 6 

